AMD is dressing up a new ATI Radeon SKU to go to office soon. The Radeon HD 4730 beats our guesswork, and wits both in one shot. The new SKU is not based on a scaled-down 40 nm RV740 GPU the HD 4770 is based on, but rather on a new RV770 variant, dubbed the RV770CE. This GPU is physically identical to the RV770, and has part of its configuration identical to the RV770LE (Radeon HD 4830), while its memory interface is 128-bit GDDR5 instead of 256-bit GDDR3.

The only explanation we have in store is that perhaps AMD is looking to save on using lesser number of memory chips per board (while not crippling the memory interface), and that RV770 is in healthier stock than the RV740. Pictured below is the PowerColor Radeon HD 4730 PCS, one of the first cards based on the GPU. Other important specifications, such as stream processor count, and clock-speeds are yet to surface. Ideally it should cash-in on a price-segment below that of the Radeon HD 4770.

ATI kicks its own ass by overcrowding the market with too many different card models. I go to CompUSA all the time and all the ATI cards I see on the shelves next to nVidia cards are a bunch of model numbers I don't recognize at prices I'd never pay for such low performance.

cause rv770 is available..... 4890s are basicly replacing 4870s and the 4770s are replacing the 4830/4850s so thats a ton of rv770 cores that are less in demand.

Now the second issue is the $100 videocard market is booming, and ATI cant keep up with 4770 demand, so putting GDDR5 on the 4830 makes it pricewise and performancewise slightly under the 4770 to fill that gap.

I say its the perfect card for OEM systems cause this will be a limited run.

I'm pretty sure that they're doing it because we're at the point where a 128bit bus board with gddr5 is cheaper than 256bit with ddr3

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Now that you mention it, THAT makes the most sense. Probably has nothing to do with the chip at all. ATI is just doing the proper thing and actually renaming the card when they do it -- hopefully the shady vendors who like to market 128-bit 3850's with GDDR2 will follow along.

Basically they want to reduce thier cost per card and on the other hand, consumers pay lesser.

It's typically a 4830 with 128Bit interface and GDDR5.

4830 loses to the 4770 and they're trying to clear it up since the 4800series are the top-notch in performance. It wouldn't make sense that 1 4700series could beat 1 of the 4800series in thier default settings. They're probably following to what consumers always follow, the higher the number, the better. Replacing the 4830 to 4730 is not a bad choice.

EDIT. Just noticed it's a new RV770CE. Probably they've had plans that 4830 would sell hot. Since thier 40nm processor is new, and they have plenty of RV770, they're clearing them up first.

But why not just use RV740 on the 4730? Why use RV740 on the 4770 and RV770 on the 4730? RV770 is more powerful, and more expensive to manufacture than RV740, why put it on a weaker card?

The only explanation I can think of is that they have too many defective RV770s, and want to use them up. Once they are used up, I have a feeling we will start to see RV740 based HD4730s.

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I have a feeling they have lots of RV770's left -- I don't know about them being defective, though. "Superfluous," maybe.

And are we sure the RV770LE (which is what these chips are, I know they're not using the 800-shader model) is faster than the RV740? IIRC, the 4770 was almost the same speed as the 4830, just a little slower, which led me to believe that while 128-bit memory with GDDR5 was comparable to 256-bit with GDDR3, it isn't actually faster still. (However, you just make up for that by upping the clock speeds a bit).

Being that as it may, a 4730 with a RV770LE would still be slower than a 4770 with the RV740, if just because it'll probably be clocked lower.

I have a feeling they have lots of RV770's left -- I don't know about them being defective, though. "Superfluous," maybe.

And are we sure the RV770LE (which is what these chips are, I know they're not using the 800-shader model) is faster than the RV740? IIRC, the 4770 was almost the same speed as the 4830, just a little slower, which led me to believe that while 128-bit memory with GDDR5 was comparable to 256-bit with GDDR3, it isn't actually faster still. (However, you just make up for that by upping the clock speeds a bit).

Being that as it may, a 4730 with a RV770LE would still be slower than a 4770 with the RV740, if just because it'll probably be clocked lower.

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RV770LE IS the 800 shader model. The extra shaders are just laser cut. They use defective 770's to make 770LE's. Which is what newtekie was basing his guess of AMD having a bunch of extra slightly defective 770's laying around.

That was the point behind RV740, we are wondering why they are using RV770 instead of RV740 to make cards that spec wise fit RV740 perfectly. Why use the more expensive to manufacture RV770?

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Same reason they use 65nm Phenom cores to make the X2 "Kuma" chips. They may have been more expensive to produce initially, but they have a surplus, while the same cannot be said of their newer 45nm (40nm, in this case) chips. Cutting their losses while they transition to the new process basically...

But why not just use RV740 on the 4730? Why use RV740 on the 4770 and RV770 on the 4730? RV770 is more powerful, and more expensive to manufacture than RV740, why put it on a weaker card?

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With 160 shaders cut, yes, it should be nearly identical in performance. It will likely be clocked a good margin lower though, which again, helps them use up chips that otherwise could not be shipped under old SKU's. Plus, the more GDDR5 they buy, the bigger the discount they get. When you're the only manufacturer using the stuff, the size of your orders likely has a pretty noticeable impact not only on the pricing you get, but general market pricing as well.

The only explanation I can think of is that they have too many defective RV770s, and want to use them up. Once they are used up, I have a feeling we will start to see RV740 based HD4730s.

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AMD doesn't seem to be in the rebranding business. If the supply of defective RV770's ran out and they were forced to use RV740 (ideal situation for them anyway), I have a feeling they'd phase out the 4730 and create a new 4750 SKU. Although given how long the 4830 has been around, and how resoundingly popular it was with the price-minded performance segment of the market, I'm surprised at how many defective chips they've got left. With that said, I'll now concede to those with greater knowledge of GPU design...

Is it possible for part of the memory bus to be defective? Could this strategy be somewhat like what they're doing with their 45nm CPU's, wherein the X3 chips have a defective core but full L3 cache, while 8xx X4 chips have all four cores but a crippled L3? If so, these could be a huge gold mine for them in that they're making use of chips that could not be marketed under the 4830 SKU, but can be under this new one without suffering from decrepit performance due to the bandwidth advantage of GDDR5. Please correct me if I'm wrong on this, but that would be interesting to say the least, and makes me wonder what nVidia/Intel do with all their defective silicon...

[EDIT] Thanks to devguy for pointing out the dual PCI-E connectors... Question: WTF? [/EDIT]
[EDIT] Also umm... Why is the 4730 getting aftermarket coolers before the 4770? I feel like they're purposefully holding manufacturers back on that, but I can't for the life of me figure out why. [/EDIT]

@aj28
We are pretty much saying the same thing, if you read my original post, that is exactly what I am saying. The practice has been used for decades in the computer world.

What I don't agree with is the name. To me RV770 should be a HD48XX product, RV740 should be a HD47XX product, and RV730 should be a HD46XX product. If they are going to release another SKU using the RV770, call it something like HD4820...